1. Field of the Invention
The invention relates generally to a voltage regulation circuit, and more particularly, to a voltage regulation circuit having a source follower.
2. Description of Related Art
A power supply is an important component of a portable device such as a mobile phone. Generally speaking, a source voltage of the portable device is typically provided by a battery. Moreover, to limit power consumption and enhance system stability with regards to an internal digital circuit, the portable device typically employs a voltage regulation circuit to perform voltage level adjustments of the source voltage provided by the battery, thereby fixing an operational voltage of the digital circuit to a predetermined value.
The voltage regulation circuit fixes the source voltage outputted by the power supply to a predetermined voltage value and thereafter provides the regulated voltage for the internal circuitry. A conventional voltage regulation circuit has an external stabilizing capacitor to prevent an overly large instantaneous response current in the digital circuit, and moreover to meet a stability requirement. However, the external stabilizing capacitor usually increases a physical size and a production cost of the system.
Therefore, in order to reduce the physical size and the production cost, how to implement a voltage regulator without requiring an external stabilizing capacitor has become an imperative issue for the design of the power supply in the portable device.